The increasing complexity and demands of assembly operations in manufacturing has been shown to lead to increased cognitive load in assembly workers. Previous work has outlined the complexity of an assembly worker's situation both in terms of difficulty and speed of work and there have been a few attempts at creating frameworks and methods for understanding the key aspects of what creates increased cognitive load. This paper presents a tool for assessing cognitive load in manufacturing, primarily assembly. The paper presents the method and an accompanying tool as well as some insights derived from this method development. The intended contribution of the work is to make a difference in reducing the cognitive load of assembly workers on the shop floor, thus focusing the development on applicability and usability of the tool in practice.